Water Pump Kit with Housing for Mercury/Mariner/Tohatsu 9.9–20 HP EFI – Replaces 8M0137849 and 8M0135821
Water Pump Kit with Housing for Mercury/Mariner/Tohatsu 9.9–20 HP EFI – Replaces 8M0137849 and 8M0135821 is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
Delivery and Shipping
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Water Pump Kit with Housing for Mercury/Mariner/Tohatsu 9.9–20 HP E...
Water Pump Kit with Housing for Mercury/Mariner/Tohatsu 9.9–20 HP EFI – Replaces 8M0137849 and 8M0135821 is backordered and will ship as soon as it is back in stock.
Product Details
This complete Water Pump Kit with Housing for Mercury/Mariner/Tohatsu 9.9–20 HP EFI is intended for servicing the lower-unit cooling system. The listing identifies this aftermarket kit for Mercury and Mariner 9.9–20 HP 4-Stroke EFI outboards from 2013 and later, as well as Tohatsu and Nissan MFS15E and MFS20E 4-Stroke models.
The kit is listed as a replacement for Mercury references 8M0137849, 98-8M0135821, 8M0134484 and 46-8M0122064, and Tohatsu/Nissan references 3RS-87322-1 and 3RS-87322. Confirm the engine model, year, serial number and original pump configuration before ordering.
- Installs in the lower unit to service the outboard cooling-water pump.
- Includes a replacement housing, impeller, wear plate, insert cup, gaskets, key and seal components as listed below.
- Uses marine-oriented replacement materials for normal freshwater and saltwater service.
- Aftermarket replacement product; it is not manufactured by Mercury, Mariner, Tohatsu or Nissan.
Part Number Matrix
Use these references to compare the listed OEM and manufacturer part numbers with the number on your original water-pump assembly.
| Brand | Part Number |
|---|---|
| Mercury | 8M0137849 |
| Mercury | 98-8M0135821 |
| Mercury | 8M0134484 |
| Mercury | 46-8M0122064 |
| Tohatsu/Nissan | 3RS-87322-1 |
| Tohatsu/Nissan | 3RS-87322 |
Engine & Model Compatibility
The application information below follows the supplied product listing. Compatibility depends on the complete model and serial-number range, not horsepower alone. Verify your engine identification label and compare the original pump assembly before purchase.
For Mercury and Mariner applications, the listed range is 9.9–20 HP 4-Stroke EFI outboards from 2013 and later, including the serial-number ranges shown below. For Tohatsu and Nissan applications, the listed models are MFS15E and MFS20E 4-Stroke outboards from 2013 and later.
| Brand | Model | Rated HP | Stroke | Years | Reference Part No. | Notes |
|---|---|---|---|---|---|---|
| Mercury | 9.9 HP EFI | 9.9 | 4-Stroke | 2013+ | 98-8M0135821 | Serial 1R00814+ |
| Mercury | 10 HP EFI | 10 | 4-Stroke | 2013+ | 98-8M0135821 | Serial 0R833820+ |
| Mercury | 15 HP EFI | 15 | 4-Stroke | 2013+ | 98-8M0135821 | Serial 0R833820+ |
| Mercury | 20 HP EFI | 20 | 4-Stroke | 2013+ | 98-8M0135821 | Serial 0R833820+ |
| Mercury | 9.9 HP EFI ProKicker | 9.9 | 4-Stroke | 2013+ | 98-8M0135821 | Verify the complete serial number. |
| Mercury | 15 HP EFI ProKicker | 15 | 4-Stroke | 2013+ | 98-8M0135821 | Verify the complete serial number. |
| Mercury | 20 HP EFI ProKicker | 20 | 4-Stroke | 2013+ | 98-8M0135821 | Verify the complete serial number. |
| Mercury | 9.9 HP EFI SeaPro | 9.9 | 4-Stroke | 2013+ | 98-8M0135821 | Verify the complete serial number. |
| Mercury | 15 HP EFI SeaPro | 15 | 4-Stroke | 2013+ | 98-8M0135821 | Verify the complete serial number. |
| Mercury | 20 HP EFI SeaPro | 20 | 4-Stroke | 2013+ | 98-8M0135821 | Verify the complete serial number. |
| Tohatsu | MFS15E | 15 | 4-Stroke | 2013+ | 3RS-87322-1 | Confirm the original pump assembly. |
| Tohatsu | MFS20E | 20 | 4-Stroke | 2013+ | 3RS-87322-1 | Confirm the original pump assembly. |
| Nissan | MFS15E | 15 | 4-Stroke | 2013+ | 3RS-87322-1 | Confirm the original pump assembly. |
| Nissan | MFS20E | 20 | 4-Stroke | 2013+ | 3RS-87322-1 | Confirm the original pump assembly. |
Technical Specs
- Product Type
- Water Pump Repair Kit with Housing
- Installation Location
- Lower unit
- Housing Material
- Marine-grade nylon
- Housing Color
- Black
- Impeller Material
- CR neoprene
- Wear Plate Material
- 316 stainless steel
- Product Category
- Aftermarket replacement
- Warranty
- 1 year against manufacturing defects under normal operating conditions, subject to the applicable warranty terms.
What’s in the Box
- 1 × Impeller, listed as 334-65021 / 3LD-65021
- 1 × Water pump housing
- 1 × Insert cup
- 1 × Wear plate
- 2 × Gaskets
- 1 × Impeller key
- 1 × Seal kit
- 1 × Installation instructions
Installation Notes
- Disconnect the battery and place the outboard in neutral.
- Remove the lower unit from the driveshaft housing according to the engine manufacturer's service procedure.
- Place the lower unit on a stable workbench and remove the fasteners securing the water-pump housing.
- Remove the old housing, impeller and wear plate. Note the original impeller-vane orientation.
- Clean the mating surfaces and driveshaft, removing old gasket material and sealant.
- Install the new gasket and wear plate in the correct order.
- Install the impeller key, then slide the impeller onto the driveshaft while turning it in the correct direction to seat the vanes.
- Install the insert cup and position the new housing over the impeller assembly.
- Install and tighten the housing fasteners evenly using the manufacturer's torque specifications.
- Reinstall the lower unit, ensuring that the water tube and shift shaft are correctly aligned. Test the cooling-water telltale before normal operation.
Troubleshooting & FAQ
How do I confirm that this kit fits my engine?
Check the engine brand, exact model, horsepower, stroke, model year and complete serial number. The listed application is for Mercury and Mariner 9.9–20 HP 4-Stroke EFI models from 2013 and later, including the serial ranges shown on this page, plus Tohatsu and Nissan MFS15E and MFS20E 4-Stroke models. If the model or serial number is outside the listed range, compare the original water-pump assembly and consult the manufacturer's parts information before ordering.
What are common signs of a failing water pump?
Possible symptoms include overheating at idle or low speed, a weak or missing telltale-water stream, or a damaged, melted or heavily scored pump housing. Stop operating the engine if it overheats and investigate the cooling system before further use.
When should the impeller be replaced?
The impeller is a regular-maintenance item. Replacement intervals vary with the engine manufacturer's recommendations, operating hours and storage conditions. Inspect it regularly and replace it if the vanes are cracked, permanently set, torn or otherwise damaged.
Should I replace the complete kit or only the impeller?
Replacing the housing, wear plate, gaskets and seals together with the impeller can help restore the complete pump assembly when these parts show wear. If the existing housing and plate are in good condition, follow the service procedure and manufacturer's recommendations for your engine.
Is this an OEM kit?
No. This is an aftermarket replacement kit. The OEM and manufacturer part numbers shown on this page are reference numbers for application comparison only and do not indicate that the product is manufactured by Mercury, Mariner, Tohatsu or Nissan.
How fast do you ship and what is the shipping cost?
Standard shipping is offered at no additional charge in the applicable regions. Typical transit time is approximately 5–15 days, although actual delivery time varies by destination, carrier and customs processing. Available expedited options and costs are shown at checkout when offered.
What is the warranty and return policy?
The listed warranty is one year against manufacturing defects under normal operating conditions. Returns are subject to the applicable return policy and normally require the item to be unused and in its original condition. Contact customer support for current warranty and return instructions.
Safety & Important Information
- Verify the engine model, year, stroke, serial number and original part before ordering.
- Compare the pump housing, impeller, keyway and gasket layout with the existing assembly.
- Follow the manufacturer's service manual and torque specifications during installation.
- Do not operate the outboard if it overheats or does not produce a normal cooling-water telltale stream.
- This is an aftermarket replacement product, not an OEM component.
- Professional installation is recommended when the correct procedure or fitment is uncertain.
About Sea Sierra
- Pro-Grade Standards — We supply marine replacement parts selected for dependable service in real-world conditions.
- Fast Global Fulfillment — Standard delivery is available to most regions, with typical transit times of 5–15 days.
- Manufacturer-Direct Value — Competitive pricing with attention to materials, fit and quality control.
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